A metaphor was a term or phrase used to make a comparison between two common things that were not alike. Synonymous terms included analogy or figure of speech, in which colorful metaphors might be used to express emotion.

Idioms had phrasing that had figurative meaning often unrelated to the actual phrasing, while proverbs were commonly sourced from folklore, historical allusion, or tribal memories.

When convinced by Kirk and Spock to draw the Companion out into the open so that it could be neutralized, Zefram Cochrane recalled the term "Judas goat," as he regretfully knew that he was leading the Companion into a trap. (TOS: "Metamorphosis")

In 2373, upon Tom Paris saying to B'Elanna Torres that he wouldn't mind seeing her Klingon side again, Torres warned him to be careful what he'd wished for. (VOY: "Blood Fever")

In 2377, when 204 Klingons came aboard Voyager, Torres said that she should be careful what she wished for, after six years of feeling uncomfortable being the only Klingon aboard for. (VOY: "Prophecy")

To be "caught with one's hand in the cookie jar" was to be found to be accessing something that was not one's own.

In, Trip Tucker had Hoshi Sato decrypt a message from the Vulcans and found it was a personal letter meant for T'Pol. When expressing his embarrassment at having inadvertently snooped on her private business, he said that he felt as though he had been caught with his hand in the cookie jar. (ENT: "Breaking the Ice")

In 2372, Torres described establishing communication with a duplicate of the USS Voyager by getting them to recalibrate their comm frequency carrier wave before they'd first made contact as "the chicken and the egg." (VOY: "Deadlock")

This term referred to something that was offered to someone in a rather obvious manner.

In 2375, Neelix offered B'Elanna Torres the chance to insult his cooking by telling her to name her poison. After she missed that chance, he seemed disappointed, claiming he'd handed it to her on a silverplatter. (VOY: "Extreme Risk")

"I couldn't fill your shoes" was a Human idiom, describing one being in a bad situation, which the other person couldn't bear.

In 2286, Leonard McCoy told Spock, when he suffered from memory loss after being resurrected, "What I mean is I may have carried your soul, but I sure couldn't fill your shoes," to which Spock replied, "My shoes?" (Star Trek IV: The Voyage Home)

"May God have mercy upon your soul" was a phrase used in some ancient Earth cultures upon sentencing a person to execution. It was used in that capacity during Worf's 2371 promotion ceremony, which included holodeck roleplaying on an sea vessel and involved him walking the plank. (Star Trek Generations)

A variant of the phrase, "May God have mercy on our souls," was used by Malcolm Reed to end his final log entry when stranded in Shuttlepod 1 and he believed there was no chance of rescue. (ENT: "Shuttlepod One")

Later in the episode's script, just after Kirk decides to search Taurus II for the Galileo, Ferris disapprovingly commented, "You said something about a needle in a haystack. Useless..." and Kirk replied, "Not if you want your needle back."

In 2364, William Riker described searching Starfleet records for an instance of someone showering in their clothes as "like looking for a needle in a haystack." (TNG: "The Naked Now")

"A penny for your thoughts" was a Human idiom, meaning that someone was curious about what the other person was thinking.

In 2368, Doctor Beverly Crusher used the expression when she wanted to get Jean-Luc Picard to talk to her during a conversation. When Picard asked her if she has one, she told him that the replicator probably has it on file. (TNG: "The Perfect Mate")

In 2369, when Q brought back Picard to the incident at Starbase Earhart in 2327, he told him (acting as a bartender): "Penny for your thoughts? You never told me you were such a lady's man," also jokingly referring to Picard's unsuccessful date with Penny Muroc. (TNG: "Tapestry")

Doctor Leonard McCoy managed to convince Dr. Nichols to accept the formula for transparent aluminum as compensation for his services by saying that once he figured out the dynamics of the matrix (which would take years), he'd be rich beyond the dreams of avarice. (Star Trek IV: The Voyage Home)

"Stone knives and bearskins" was a colorful term employed by Spock to describe the 1930stechnology he was forced to use to construct a tricorder interface. Vital information was locked within Spock's tricorder: How had Leonard McCoy changed history? Spock was eventually able to construct an appropriate circuit, but retrieved two separate recordings: one in which Edith Keeler lived, and one in which she died. At that point, the improvised interface erupted in sparks and flame, ruining his chance to learn which of the recordings represented McCoy's alteration, and which the correct timeline. (TOS: "The City on the Edge of Forever")

"Wash my hands of it" was an expression used to avert a wrong decision, claiming that the person could not be held responsible for it. It came from the Bible, and was said by Pilate after he sentenced Jesus Christ to crucifixion, as demanded by the crowd; however, Pilate saw he was apparently innocent.

In 2367, Data told Doctor Crusher that he "could be chasing an untamed ornithoid without a cause," describing this idiom, when examining the clues of AmbassadorT'Pel's presumed death. Crusher eventually recognized the idiom, and corrected him with its common form. (TNG: "Data's Day")

Finding a second wind meant regaining energy after a certain activity had gotten tired.

During a 2153 engine test aboard Enterprise, field fluctuations dropped to zero, which lead captain Archer to suggest that they had gotten their second wind. That impression was incorrect. (ENT: "Similitude")